Method of and apparatus for calcining plaster.



No. 781,747. 7 I PATENTED FEB. 7, 1905;

F. A. SIMONDS.

METHDD OF AND APPARATUS FOR GALCINING PLASTER.

APPLlOATION FILED MAY 16. 1904.

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No. 781,747. PATBNTED FEB. 7, 1905.

P. A. smonns.

METHOD OF AND APPARATUS FOR GALCIN I NG PLASTER.

APPLIOATION FILED MAY 16. 1994.

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I a UNITED STATES Patented February 7, 19. s.

PATENT OFFICE.

FRANK A. SIMONDS, OF GRAND RAPIDS, MICHIGAN, ASSIGNOR OF ONE- HALF TOADOLPH LEITELT IRON WORKS, OF (irRANl) RAPIDS, MICHI- 'GAN, ACORPORATION OF MICHIGAN.

."METHOD OF AND APPARATUS FOR CALCINING PLASTER.

SPECIFICATION forming part of tters Patent No. 781,747, dated F l' l'j7, 1905.

Application filed Kay 16,1904. Serial No. 208,166.

To all. whom it may concern.- Be it known that I, FRANK A. SIMONDS, acitizen of the United States, residing at Grand Rapids, in the county ofKent and State of 5 Michigan, have invented certain new and usefulimprovements in Methods of and Apparatus for ()alciniug Plaster; and Ido hereby declare the following to be a full, clear, andexactdescription of the invention, suchas will to enable others skilledin the art to which it appertains to make and use the same.

My invention relates to an improved method of calcining plaster andapparatus for the same; and its object is to provide means for I5operating continuously upon a constantlyflowing stream of plaster.

Heretoforeit has been found diflicult to ca]- cine plaster by anycontinuous process, the result being that the plaster would either be 2heated too much or not enough, and no adequate means of regulating thetemperature to properlydo the work has been devised. Before calcining,plaster contains water in two different states, the free moisture andthe 'water of crystallization. The former is rapidly driven off at-atemperature of about 212 Fahrenheit, after which it requires aconsidcrably higher temperature to break up the crystallization anddrive the water out of the same-namely, about 300 Fahrenheitand if suchheat is applied beyond the necessary extent the plaster becomes overdoneand is injured thereby, producing what is commonly known as burntplaster.

My improved process consists, essentially,

in applying steam heat to a continuouslyflowing stream of plaster andregulating the heat applied to the different portions of the stream bymeans of regulating the pressure 4 .of the steam and in adjusting theheat applied to the plaster during the latter part of the operation toonly a slight degree above the calcining temperature, and thus avoidingany ex-- cess of heating after the water of crystalliza-.

tion is driven off.

Referring to the accompanying drawings, which represent a form ofapparatus adapted to perform my improved process, Figure 1 represents aside elevation of the device; Fig. 2,'an end elevation of the same withparts 5 broken away; Fig. 3, an enlarged detail in vertical section onthe line 3 3 of Fig. 2, and Fig. 4 an elevation of one head of acylinder. Like numerals refer to like parts in all of the figures.

1, 2, and 3 represent a series of heating-cylinders, through whichplaster passes in the process of calcining. These cylinders are rotativeand inclined, whereby the plaster is stirred and brought in-contact withthe inte- 6o rior of the cylinder and passes slowly from end to endthrough the same. The upper end of each cylinder is provided with a.receivingcase (shown at 4, 5, and 6) to receive the plaster at thebottom and to collect and discharge 6 5 the vapor therefrom at the top,each case being provided witha suitable discharge-pipe 30 to convey awaythis vapor. The lower end of each cylinder is provided with adischarge.- case. (Shown at 7, 8. and 9.) The plasterto be calcined issupplied to the case 4 through I any suitable spout 10, and thedischarge-case 7 of the first cylinder is connected to the bottom of thereceiving-case 5 of the second cylinder by a -uitable curved spout 11,and in like manner the discharge-case 8 of the second cylinder isconnected to the bottom of the receiving-case 6 of the third cylinder,and the discharge-case 9 of this last cylinder is provided with asuitable spout 13 to discharge the finished product. Each cylinder isconstructed of two concentric tubes 21 and 22 of unequal diameter andspaced apart to provide a steam-receiving space therebetween. This spaceis closed at each end by suitable rings 8 '23, securely riveted in placebetween the tubes and provided with suitable openings 24 to receivesteam and discharge water. v

The cylinder-heads consist of suitable rings 25, closely fitted to therings 23 and secured o thereto, and curved hollow arms 26, extendingfrom opposite the openings 24 to tubular' hubs 18, forming the journalson which the cylinders rotate. These hubs are provided with suitablestufiing-boxes in which are inserted pipes to convey steam to thecylinders and to convey condensed water therefrom through the hubs,arms, and openings in the rings. Each cylinder is provided at its upperend with a steam-pipe 14, inserted in the hub 18, and interposed in eachpipe is a throttlevalve 15, a pressure-regulating valve 16, and apressure-gage 17, whereby the operator can accurately determine thepressureof steam in each respective cylinder. In the hub at the lowerend of each cylinder is inserted a pipe 19 to convey away the water ofcondensation to suitable steam-traps 20, which remove the water andretain the pressure of steam in each respective cylinder. Each cylinderis also provided with means for rotating the same, which in thisinstance are shown as bevelgears 28, attached to one of the journals ofeach cylinder, and suitable pinions 29, engaging the same, which pinionsmay be operated in any convenient manner. Each receivinghead is providedwith buckets 27 attached thereto, which buckets are adapted to rotatewithin the respective recei ring-case and take up the plaster in thebottom of the same and discharge it into the interior of the respectivecylinder. These buckets have inwardly-curved inner ends to laterallydischarge the material into the cylinder, as shown in Fig. 3, and thearms 26 in the lower heads are so curved that they will scoop up thewater and convey the same to the hub.

The operation of this device in performing my improved process is asfollows: The plaster to be calcined is regulated in its flow through thespout 10 in any convenient manner and passing through the cylinders isthoroughly stirred and brought into intimate contact with the heatedinner walls of the same. Escaping at the lower end of the firstcylinder, it passes through the spout 11 into the receiving-case 5 andpassing through the second cylinder is discharged through the spout l2and iinaily passes through the third cylinder and is discharged at thespout 13. During its progress through these various cylinders it may be.exposed to dill'erent temperatures in each, according to the pressure ofthe steam admitted to the respective cylinders. By spouting the plasterinto the bottom of the receiving-cases and taking it up in the curvedbuckets and discharging it into the lower side of the cylinder there isbut little tendency to its escape in the form of dust through the pipes30. It is immaterial what the temperature may he until the free moistureisdriven olf; but it is essential that the temperature shall beregulated so that while the plaster is sutiiciently heated to 41 riveoff the water of crystallization it shall not he overheated, and forthis purpose the temperature in the lower cylinder or cylinders, wherethe finishing is done, is maintained at substantially the same as or atonly slightly above the calcining temerature. The result is that howeveriong ter of crystallization has been drivbn oil" the plaster will not beoverdone and injured by excessive heat, and by the use of steam atHaving thus fully described my invention,

what I claim, and desire to secure by Letters Patent, is-

l. The improved method of calcining plaster, consisting of applyingsteam heat to a continuously-moving stream of plaster, and regulatingthe temperature of the steam to substantially the calcining temperatureof the plaster by regulating the pressure of the steam.

2. The improved method of calcining plaster consisting of passing acontinuous stream of plaster through a series of steam-heated vessels,regulating the temperature of the heating-steam by regulating thepressure thereof and adjusting the temperature of the last vessel in theseries to near the calcining temperature of the plaster.

3. The improved method of calcining plaster consisting of passing acontinuous stream of plaster through a series of stean'i-jacketed andinclined rotating cylinders, supplying steam to said cylinders to heatthe same, regulating the pressure of the steam'to determine thetemperature thereof, and adjusting the temperature of the last vessel inthe series to near the calcining temperature of the plaster.

4. An apparatus for calcining plaster comprising a series ofsteam-heated vessels, means for passing a continuous stream of plastersuccessively through the said vesseis, means for separately supplyingsteam to the same and removing the water of condensation therefrom, andmeans for separately adjusting the pressure of the steam to adjust thetemperature of each vessel.

5. The combination of a series of inclined rotative cylinders havingdouble walls spaced apart, means for supplying steam to the spacesbetween said walls, means for removing the water condensed therein. aseparate steampipe for each cylinder, at tln'ottle-valve, apressure-regulating valve and a steam-gage in each pipe, a separatedrain-pipe to each cylinder, and a steam-trap to each drain-pipe.

6. In a calcining apparatus. a cylinderhaving double walls spaced apart,rings closing the ends of said spaces and having perforationsilltl'trtlllOULfll, heads attached to the rings and comprising hollowarms opposite said openings and tubular hubs, a steam-pipe inserted inone of the hubs, a. (,lrain-pipe insertcd in t be other hub, asteam-trapconnccted to tlwdrain-pipe, a pressure-gage, apressureregulating valve, and a throttie-valve in the steam-pipe, andneans for passing plaster through the interimot' the cylinder.

the treatment may be continued after th wa- I i". inacalciningapparatus.a strain-jac-lieu-d rotative cylinder, means for regulating the pressureof steam in the same, a receivingcase inclosing one end of the cylinder,buckets attached to the cylinder and rotative in the case, adischarge-case inclo'sing the other end of the cylinder, means forconveying plaster to the receiving-case, and means for conveying plasteraway from the discharge-case.

8. In a calcining apparatus, the combination of a cylinder having doublewalls spaced apart, rings closing the ends of said spaces and havingperforations, heads comprising hollow arms opposite said perforations,and hollow hubs connected to said arms, means of supplying steam to onehub, means for conveying water away from the other hub, a receiving-casesurrounding one head, curved buckets attached to said head and havinginwardly-curved ends and rotative in the case, a discharge-casesurrounding the other head, a spout connected to the discharge-case, andmeans for regulating the pressure of the steamsupply.

9. In a calcining apparatus, the combination of a series of inclinedrotative and steamjacketed cylinders, means for supplying steam to thesame, means for severally regulating the pressure of steam in saidcylinders, a reinclined cylinder having double walls spaced apart, ringsclosing the ends of said spaces and having perforations, a head attachedto the lower end of said cylinder and comprising curved hollow armsopposite said openings, and a hollow'hub' connected to said arms, a headconnectedto the upper end of said cylinder and having hollow armsopposite the openings in the ring, and a hollow hub con nected to saidarms, a drain-pipe connected to the lower hub, a steam-pipe connected tothe upper hub, and means for regulating the pressure of steam admittedto the cylinder.

In testimony whereof I afiix my signature in presence of two witnesses.

v F EANK A. SIMONDS.

Witnessesz" LUTHERv V. MoUL'roN, WARRE W. ANNOBLE.

